In recent years, a compact, light-weight, high output and high energy density organic electrolyte battery is attracting attention as a secondary battery, and lithium ion secondary battery has become the mainstream. A sealant to be used therefor is a very important material that shuts off the organic electrolytic solution from the moisture of the outside world.
As a resin-based sealant, for example, polyolefin-based adhesive (patent document 1), polyvinylidene fluoride resin (patent document 2) and the like have been conventionally used.
In lithium ion secondary battery to be used as a drive battery of vehicles such as electric automobile (EV), hybrid electric automobile (HEV) and the like, improvement of the heat resistance of the battery has become an important problem to ensure long-term reliability of the battery. Therefore, stainless steel and nickel, which are high-heat-resistant metals, have been considered for a collector and an electrode terminal (tab) of an electrode, instead of aluminum conventionally used widely for lithium ion secondary battery, and a sealant to seal a battery is required to show superior adhesiveness to not only aluminum but also high-heat-resistant metal such as stainless steel, nickel and the like, and further required to show organic solvent-resistance that maintains adhered state even in contact with an organic electrolytic solution at a high temperature.
When an organic electrolyte battery such as lithium ion secondary battery and the like is used as a drive battery of a vehicle such as electric automobile, hybrid electric automobile and the like, the battery needs to have high capacitance and high voltage. In this case, stacked parallel battery and stacked series battery equipped with plural electric power components are advantageous. When the number of the electric power components is increased, however, the total thickness of the stacked battery increases, leading to scaling up, and the need arises to make electric power components (stacked unit of positive electrode/electrolyte layer/negative electrode) thinner. As a result, the gap between two pieces of collectors sandwiching an electric power component becomes narrower, and a highly reliable sealed structure is becoming difficult to form with conventional sealants such as polyolefin-based adhesive, polyvinylidene fluoride resin and the like.
The material used for an electrolyte layer to be interposed between a positive electrode and a negative electrode is not generally provided with high heat resistance. As a sealant to seal a gap between two pieces of collectors sandwiching an electric power component, one permitting a sealing work at a comparatively low temperature is advantageous. Thus, a sealant affording a high adhesive force to a metal at a low temperature is desired.